In the building trades, as well as in other industries, it is often necessary to configure a structural assembly in a non-uniform shape and to be able to quickly and easily move the assembly from one location to another. With specific reference to the construction industry, a scaffolding system or frame assembly is typically employed in close proximity to the building or structure being worked on, in order to provide artisans with a suitable area from which to perform their tasks. These tasks cover all aspects of a structure's construction and maintenance, including such diverse activities as applying materials to buildings under construction, washing the windows and exterior surfaces of completed buildings, and sandblasting and repainting the metal surfaces of bridge members.
In the past, scaffolding systems were constructed by bolting together vertical and horizontal members, and were essentially built from the ground up. These scaffolding systems were usually not movable, and therefore allowed access to only one portion of the building or structure at a time. To move on to the next portion of the building, it was usually necessary to disassemble the scaffolding system, relocate its base, and then reassemble the members involved. In addition to requiring a considerable amount of time and energy to dismantle and reassemble the scaffold each time it was moved, these prior art systems also presented significant safety risks to the workers using them. In addition, for most of these prior art scaffolding systems, the vertical height of the work platform could not be raised or lowered without dismantling a substantial portion of the scaffolding system.
Another problem that has become prevalent in modern construction and maintenance activities is the need for scaffolding systems which are readily adaptable in size and shape, and which can be easily configured to accommodate a variety of accessories. As the pace of building construction has increased, and the time available for completing each task has correspondingly decreased, such scaffolding systems have become key elements in the construction process. The variety and complexity of building shapes and structures has increased dramatically in recent years. Designing and fabricating customized scaffolding systems to fit particular building shapes and to accommodate particular tasks can be both time consuming and relatively expensive. Contemporary scaffolding systems must therefore be adaptable for use in many configurations and applications. The assembled platforms must also have sufficient span strength and torsional rigidity to safely hold both the workers using the scaffolding and their materials.
Recently, several scaffolding system improvements have been disclosed which alleviate a number of the problems noted above. U.S. Pat. No. 4,234,055, issued to G. L. Beeche on Nov. 18, 1980, describes a mobile suspension scaffold which requires assembly and dismantling only once for each construction site, at the beginning and the end of the job, respectively. The system described may be moved along the sides of a building and around building corners without being disassembled. A suspended scaffold system which may be used either independently or in conjunction with this mobile scaffold is the folding scaffold described in U.S. Pat. No. 4,253,548, issued to G. L. Beeche on Mar. 3, 1981. The system disclosed therein includes a plurality of work platforms which are foldably linked together. U.S. Pat. No. 4,967,875, issued to G. L. Beeche on Nov. 6, 1990, described a scaffolding system which employs modular components that may be combined to readily provide a variety of scaffold configurations and sizes. U.S. Pat. No. 5,203,428, issued to G. L. Beeche on Apr. 20, 1993, in turn discloses a scaffolding platform comprised of connected truss frames, which platform is particularly useful in conjunction with the scaffolding system disclosed by U.S. Pat. No. 4,967,875, and which may also be used independently thereof. The scaffold platform set forth in U.S. Pat. No. 5,203,428 is itself modular in nature, thereby further facilitating the assembly of scaffolding platforms which can conform to nearly any building size or shape. Finally, U.S. Pat. No. 5,214,899, issued to Beeche et al. on Jun. 1, 1993, describes a truss frame that is assembled from lightweight, modular components which are designed so as to provide the assembled frame with exceptional strength and rigidity.
For these and other commercially available scaffolding systems, the strength provided in the vertical and horizontal directions must be traded off against the amount of material used in the structural members, and, correspondingly, the cost and weight of those members. Another factor which must be considered is the availability and complexity required for components used to attach the scaffolding members to other structures.
In typical scaffolding applications, structural members are subject to both vertical load forces and horizontal deforming forces, produced, in part, by reaction to the load forces. For any given situation, either the vertical and horizontal strength provided by the structural member must be sufficient to withstand such forces, or appropriate additional bracing of the member must be incorporated into the scaffold design.
A cylindrically-shaped tube provides equal strength in the vertical and horizontal directions, so it does not need bracing to increase its horizontal strength. However, most scaffolding applications do not require equal amounts of horizontal and vertical strength, and a cylindrical design is therefore inefficient in that the member includes more metal material in certain locations than is necessary. Furthermore, the cylindrical shape of the member requires the use of special, non-standard accessories for such items as trolleys and building column mounts, which are relatively costly compared to available, off-the-shelf components.
Similarly, a square-shaped tube provides equal strength in both directions. Once again, however, since equal strength is usually not required in both the horizontal and vertical directions, such a member is also an inefficient use of metal material. To remedy that problem, a rectangularly-shaped tube may be formed. Doing so results in a non-symmetrical shape which reduces the modularity of the structural member. More importantly, a square-shaped or rectangularly-shaped tube presents its own difficulties with respect to attaching the members to like members and to other components. For example, in trolley/track applications, it is relatively difficult to attach the member to building columns without interfering with trolley travel.
Conventional I-beams provide significantly higher vertical strength than horizontal strength, and the top and bottom flanges incorporated therein provide better accessibility for attachments. However, because a conventional I-beam uses only a single web member between the flanges, the horizontal strength provided is significantly less than that provided by a square-shaped or rectangularly-shaped tube (both of which essentially have two web members).
What is needed, then, is a structural member which combines the desirable features of each of these prior art devices, one which makes an efficient use of the metal material while providing sufficient strength in both directions, and which provides ready access for connecting both like members and conventional accessories.
Accordingly, it is an object of the present invention to provide an improved structural member having increased horizontal strength compared to conventional I-beams, while utilizing an equivalent amount of material.
It is another object of the present invention to provide a structural member which is readily useable with conventional accessory components, such as trolleys and building infrastructure elements.
It is a further object of the present invention to provide a structural member for which the vertical and horizontal strength thereof may be increased by adding removable, cooperating modular components, so as to form a modular beam system wherein the same standard components are useable for multiple applications requiring varying member strengths.
It is also an object of this invention to provide a structural member which is readily and easily attachable to like members, both in an end-to-end relationship and in a perpendicular relationship.
It is an additional object of the present invention to provide a structural member and associated components which may be assembled in a modular fashion to form scaffolding systems having varying shapes, sizes, and strength characteristics.